Study On Base Isolation Performance Of Multi-story Steel Framework Structures

In recent years,the effectiveness and superiority of base isolation technology in building seismic resistance have been widely recognized.As a new idea of building seismic resistance,base isolation technology has been more and more widely applied in the newly-built buildings and old buildings' reinforcement and transformation of masonry structures,concrete structures and steel structures in worldwide countries.At present,the structures of the isolated buildings in China are mainly composed of multi-storey masonry structures and reinforced concrete structures.And so far,steel structure isolated buildings are still rare,relatively.In addition,at present,China's base isolation technology is still in the stage of promotion and application,the isolation form is still single,the building structure form in which isolation technology is used is not comprehensive.Laminated rubber bearing isolation system is the most widely used seismic isolation system in our country and even in the world.Therefore,based on the finite element theory and dynamics principle,the paper studies the seismic performance of base isolated multi-layer steel frame structure with lead rubber bearings,providing some reference for the application and promotion of base isolation technology in steel structure.The main research contents are as follows:A multi-layer steel framework structure engineering example was cited.Lead rubber isolators were selected as isolation bearings and their specific model and quantity were identified through calculation according to the requirements of codes and specifications.The 3-D finite element models of the non-isolated and base-isolated structures with lead rubber bearings of the multi-storey steel frame building were established by using large finite element analysis software SAP2000.Three seismic waves suitable for III sites were reasonably selected,and fast non-linear time history analysis(FAN)cases were defined.The linear dynamic time-history analysis method and the non-linear dynamic time-history analysis method were respectively used for the non-isolated structure and the base-isolated structure to calculate the horizontal and vertical seismic responses of the two structures under different seismic waves' action.Comprehensive comparative analysis on the natural period of vibration,the mode of vibration,the interlaminar shear force,the base shear,the inter-storey displacement and floor acceleration of the two structures was carried out.The analysis and research results show that the natural vibration period of the upper-structure of the base isolated multi-storey steel frame building with lead rubber bearings is obviously prolonged,and the main vibration mode is "the overall translational",the translational and torsional coupling effect is reduced,the horizontal seismic responses such as the interlaminar shear force,the base shear,the interlayer horizontal displacement,the horizontal acceleration of the floor were dramatically reduced,and the vertical acceleration of the floor is not reduced but increased.Generally speaking,the lead rubber bearing has obvious effect on reducing the horizontal seismic responses of the upper structure,but cannot isolate or reduce the vertical seismic responses.The study validated the effectiveness of the base isolation technology in the multi-storey steel frame structure,it is believed that with the further study of the project and the further promotion of the engineering application,the base isolation technology will play an important and strong role in improving China's steel structure building seismic resistance level.